Objective Finite element analysis was carried out to explore the biomechanics of mucosal responses to mechanical stimulation from the spherical self-ligating bracket and conventional bracket. Methods A three-dimensional finite element model of lip-incisor-bracket was established. Four simulated cases were designed and analyzed numerically according to different arrangements of central incisors, and the stress and strain of the moving upper lip under the spherical bracket and the conventional bracket was explored individually. Results The maximum stress of spherical bracket on mucosa was higher than that of conventional bracket when tooth was aligned. The maximum stress of conventional bracket on oral mucosa was higher than that of spherical bracket concerning that the incisor had a mesial torsion of 15° and 30°, as well as labially misaligned by 15° respectively. Conclusions Compared with the square conventional brackets, the spherical brackets with smooth shape are more suitable for the functional movement of oral soft tissue in orthodontic patients with irregular dentition. It is suggested to improve the shape design of the conventional brackets to reduce the mechanical response of oral mucosal tissue.